4. 'Sgt. Pepper's Lonely Hearts Club Band'

What more can be written about 1967's Sgt. Pepper's Lonely Hearts Club Band? Beyond the fact that it was the last time The Beatles truly worked together as a united band, it also established the LP as an art form and influenced countless rock groups that followed. "Sgt. Pepper was our greatest endeavor," Ringo said in 2000. "The greatest thing about the band was that whoever had the best idea – and it didn't matter who – that was the one we'd use."